Background: The New World vultures have been placed as a family in
the Falconiformes through most of their taxonomic history. Morphological and
behavioral data (Ligon 1967, König 1982, Rea 1983) that showed intriguing
similarities with the storks, Ciconiidae, were generally considered examples of
convergence or chance until Sibley & Ahlquist's DNA-DNA hybridization data
also supported a stork-cathartid relationship. Harshman's (1994) reanalysis of
the DNA-DNA hybridization also confirmed the conclusions of the original
analysis. Biochemical data from Jacob (1983) and Wink (1995) were also
consistent with a stork-vulture relationship. On the basis of these congruent
data sets, the AOU Checklist (1998) removed the Cathartidae to the
Ciconiiformes.

New information: Griffiths (1994) pointed out weaknesses in the
data used to support a stork-cathartid relationship, and also provided data
from syringeal morphology that were consistent with placement in the
Falconiformes. Analyses of DNA sequence data have failed to find any close
relationship between Ciconiidae and Cathartidae. The most recent of these
(Ericson et al. 2006) found that the two families are in different groups of
the Neoaves, with > 95% Bayesian support for the two nodes that define each
group. The group of orders in which the Cathartidae falls includes such diverse
groups as owls, the coraciiform assemblage, parrots, seriemas, trogons, colies,
Passeriformes, as well as the Accipitridae and Falconidae (which are not
closely related). However, the Cathartidae branch does not associate closely
with any other branch in this group. The group in which the Ciconiidae falls
includes Procellariiformes, penguins, loons, rails, cranes, bustards, most
"Pelecaniformes," cuckoos, and turacos, as well as all the herons and
ibises; parallel to the Cathartid, the Ciconiidae do not fall unambiguously
within any cluster of orders, including that which contains herons, ibis, and
pelicans. Previously, Cracraft et al. (2004) had also failed to find any
support for a stork-cathartid relationship, and in fact found some support for
a cathartid-accipitrid relationship as well as results fairly consistent with
those of Ericson et al. for placement of the Ciconiidae. Fain & Houde
(2004) found that Ciconiidae was the sister group to Ardeidae, and that these
two grouped with a cluster of groups that included Threskiornithidae,
Musophagidae, Cuculidae, Procellariiformes, and Gaviiformes; the Cathartidae
branch is part of a large polytomy and does not for certain associate with
Accipitridae or Falconidae.

Analysis and Recommendation: I think there are other analyses with similar
results albeit weaker taxon-sampling, but for the purpose of this proposal, the
above three suffice to show that sequence data that support a
Ciconiiformes-Cathartidae relationship are nonexistent, and that regardless of
the differences of the branching patterns among the studies, these two groups
are not part of the same cluster of orders. Also, support for a relationship to
any of the traditional Falconiformes (itself a non-monophyletic group) is weak
at best. To maintain the Cathartidae within the Ciconiiformes, despite the
earlier support for this relationship, ignores all recent genetic data.
Therefore, I strongly recommend removal of Cathartidae from Ciconiiformes.

For
now, this proposal asks for YES/NO vote on removal, without regard to where to
place Cathartidae. If it passes, I'll then construct a proposal for the
alternatives, namely (1) family Incertae Sedis, (2) return to traditional
position in Falconiformes, or (3) placement in their own order, Cathartiformes.
Concerning the three alternatives, I lean towards the latter because (1)
ordinal rank for New World vultures is already in use in many classifications
(1100+ hits on GOOGLE yesterday for "Cathartiformes"), (2) it
accomplishes the same thing as Incertae Sedis by removing the group from within
any existing order, and (3) New World vultures are diagnosable in fossil record
as far back as at least the Upper Eocene and thus constitute a lineage as old
as most avian bird orders. But that's for a subsequent proposal.

Comments from Stiles: "YES. After reading Griffiths and her
inability to duplicate Sibley & Ahlquist's tree, I am more inclined to
discount the cathartid-ciconiid relationship. Rather a shame, as it introduced
a nice little bit of symmetry - the ciconiid brings the baby, the cathartid
takes it away when itęs done ... all in the family (or order), as it were.. I
also lean toward Cathartiformes, as a more satisfactory alternative than
returning these birds to Falconiformes, to which their relationship is
decidedly distant."

Comments from Zimmer: "YES. I too, would support placement in a
separate order (Cathartiformes) as opposed to placement in an existing
order."

Comments from Stotz: "YES. This is long overdue. It became
clear pretty early after Cathartidae was moved into Ciconiiformes that the
characters joining it with the storks were primitive characters."